Palo Alto Water Heater Repair: Pilots, Leaks, Parts, Permits

Two wall-mounted tankless water heaters plumbed with copper supply lines. Photo: Behrat, CC BY-SA 3.0, via Wikimedia Commons.

The houses here

Old chimneys near downtown, slabs and shallow roofs in the Eichler tracts

Palo Alto's houses split repair work into two kinds. Professorville's brown-shingle houses were built for Stanford's early faculty, and where a gas heater in a house that old still exhausts into a brick chimney, the city's inspection guideline will not let a new heater reconnect to an unlined masonry flue without a listed liner. Palo Alto also has more Eichler homes than any other city, most of them in south Palo Alto, on concrete slab floors with radiant heating cast in and ceilings that follow the roofline, so a vent, a condensate line or a new circuit has few hidden routes. Where a house has a basement, the guideline wants the relief valve drain piped up and out to the exterior.

The work

Faults a Palo Alto service call tends to find

A pilot that keeps going out
Rheem's standing-pilot troubleshooting table lists the usual causes: a loose or failed thermocouple, a thermocouple sitting outside the flame, a weak safety magnet in the gas valve, a partly clogged pilot, a blocked flue, or a downdraft in the vent. Since 2009 the Air District has held standard atmospheric gas tanks of 50 gallons or less to 10 nanograms of NOx per joule of heat output, and Rheem sells a separate pilot assembly kit for its California ultra-low-NOx models, so the replacement part has to match the heater on the rating plate.
Too little hot water, or none
The same table separates parts from tanks. A thermostat set low, a clogged burner orifice, low gas pressure or a broken dip tube, which lets incoming cold water mix at the top of the tank, all leave a heater short and can be fixed. A heater that has shut itself off after overheating may have tripped its single-use energy cutoff, and Rheem's answer to that is a new gas control valve. Each is a part swap, which Palo Alto's permit-exempt list allows when the equipment's approval is unchanged.
Water on the floor that is not a leak
Rheem tells its own service staff not to approve a replacement until every possible water source has been checked. Condensation forms on cold pipes and inside a gas heater's flue while a tank of cold water heats, and the company notes that most returned heaters which then held water under test had been replaced in winter or early spring. Water that dries overnight is not a tank leak, water under the relief valve discharge points to thermal expansion, and seepage at a fitting or drain valve is a part. A shell that keeps leaking is finished.
A yellow flame or soot at the draft hood
CPAU's gas safety brochure says pilots and burners should burn with a steady blue flame, lists soot or water collecting near a burner or vent among the warning signs of carbon monoxide, and asks owners to have gas appliances, vents and flues looked at every year or two by qualified professionals. Rheem traces a yellow, floating or noisy flame to starved combustion air, a blocked flueway, wrong gas pressure or a dirty orifice. In an older house, a rusted vent connector or a chimney crumbling inside turns a burner adjustment into venting work.
A heat pump heater running on its elements
Heat pump units fail in their own ways. Rheem's bulletin on its A108 alert explains that a blocked condensate line makes the heater fall back to its electric elements, so the water stays hot while the efficiency disappears; clearing the line or replacing a faulty sensor usually ends it. Palo Alto's inspection guideline for these heaters shows what a replacement must include: a disconnect within sight, framing or a stand able to carry the weight, and the abandoned gas line terminated in an approved way.

Permits and local rules

Palo Alto rules behind the repair-or-replace call

Work exempt from permit
The Building Division's list of work needing no permit includes, under gas, replacing any minor part that does not alter the approval of the equipment or make it unsafe, and the mechanical section says the same. A manufacturer's thermocouple, pilot assembly or control valve fits that wording. The tank itself does not: the city's heat pump guideline states that a plumbing permit is required for every water heater installation and replacement, with a final inspection once the work is complete.
City of Palo Alto Building Division (opens in a new tab)
Instant Building Permit list
Instant permits are limited to licensed contractors with an active Accela Citizen Access account, and the water heater entries are narrow: one heat pump water heater at a detached house or duplex, or one gas water heater that is not tankless, carries the same number of BTUs or fewer and stays under 200,000 BTU. Anything else goes through the regular checklist, with a floor plan, the old and new locations, the gas demand and, for a tankless unit that raises it, a utilities application.
Source: City of Palo Alto Development Services (paloalto.gov)
Inspection Guidelines: Water Heater (503)
The guideline behind inspection 503 reaches past the tank. The old gas connector may not be reused, a sediment trap sits ahead of the new one, the gas shutoff stays accessible within 6 feet and a union goes within 12 inches. A heater in a closet off a bedroom or bathroom needs a listed, gasketed, self-closing door and all of its combustion air from outdoors. Any change to the gas piping beyond the connector brings a whole-house gas test.
Source: City of Palo Alto Building Inspection (paloalto.gov)

State license for this work: C-36 Plumbing, C-20 Warm-Air Heating, Ventilating and Air-Conditioning, C-10 Electrical. Look up a contractor's license on the CSLB website (cslb.ca.gov).

Timing

From a dead tank to the 503 final

How fast a Palo Alto replacement can be permitted depends on its path. An instant permit is issued through the city's portal once a contractor completes the application. A job that needs review can enter the over-the-counter pilot for residential mechanical, electrical and plumbing work: a coordinator checks the pre-application for completeness within one business day, then books a one-hour appointment, and an approved submittal leaves with its permit that day. At the final, the large-format approved plans, the printed permit card and the installation instructions must all be on site.

Before you hire

Settle these with whoever opens the burner door

Can you test the thermocouple, safety magnet and pilot, and source the matching ultra-low-NOx pilot kit for our heater's brand and size?
Before quoting a new tank, will you rule out condensation, relief valve discharge and leaking fittings?
If our heater vents into the old chimney, is a listed liner part of the quote?
For a replacement, do you hold the Accela account Palo Alto's instant permit needs, and will you fit a new gas connector?
Is your C-36 Plumbing license current at cslb.ca.gov, or C-20 if you install heat pump water heaters?

Questions

Asked about Palo Alto water heaters before anyone buys a new one

Does replacing a thermocouple or gas valve need a Palo Alto permit?

Usually not. The city's permit-exempt list covers replacing a minor part of gas equipment when the part does not alter the equipment's approval or make it unsafe, which describes a manufacturer's thermocouple, pilot assembly or control valve. Replacing the water heater itself always takes a plumbing permit and a final inspection, whether it is a like-for-like gas tank or a heat pump unit.

How can I tell how old our water heater is?

CPAU's guide starts at the label: copy the model and serial number, onto the sticker the city mailed out if you still have it. Rheem serials open with month and year, so 1209 means December 2009. Bradford White uses a letter for the year that repeats every 20 years, so a C can mean 2006 or 2026. The city suggests a gas heater more than 10 years old may be due for replacement.

Our gas heater died without warning. Can the city help replace it?

For a switch to a heat pump water heater, yes. CPAU's Electrify My Home program includes an Emergency Replacement and Fast Service option in which its Home Energy Advisor arranges the estimate, permit, installer and inspection and applies the city's rebates. Owners who would rather hire their own contractor can still claim rebates, a permit fee rebate among them, through the program's rebate hub.

Can a heat pump water heater sit outside a Palo Alto house?

It can, with two checks from the city's heat pump inspection guideline. Planning's setback rules decide where the unit may stand, and it may not make noise more than 6 decibels above the ambient level measured at the property line, under Municipal Code section 9.10.030. The guideline suggests confirming the unit's maximum noise in the manufacturer's installation manual before the spot is chosen.

If our gas heater is repaired now, will the Air District force a replacement later?

No. The Air District's zero-NOx standard covers heaters manufactured after its compliance date and applies when a new one is sold or installed, not to a heater already working, so a repaired tank can stay in service. Its Board considers moving that date for residential tanks from January 1, 2027 to January 1, 2028 at a hearing on November 4, 2026.

Keep exploring

More on water heater work and Palo Alto

Water heaters in other cities

Other trades in Palo Alto

Guides and smaller jobs

Where this page belongs

Where these facts come from

Checked against these public sources in October 2026. Rules and programs change: confirm permit requirements with the city before work starts, and a contractor's license on the CSLB website.

cityofpaloalto.org: work exempt from permit
paloalto.gov: Apply for a Building Permit (paloalto.gov)
paloalto.gov: res water heater replacement 2026 (paloalto.gov)
paloalto.gov: water heater (paloalto.gov)
paloalto.gov: electric heat pump water heater inspection checklist 07.20.2017 (paloalto.gov)
paloalto.gov: Over the Counter Residential MEP Permit Pilot Program (paloalto.gov)
paloalto.gov: Switch to a Heat Pump Water Heater (paloalto.gov)
paloalto.gov: Check Your Water Heaters Age (paloalto.gov)
paloalto.gov: Heat Pump Water Heater FAQs (paloalto.gov)
paloalto.gov: gas safety brochure2025 (paloalto.gov)
rheem.com: whtechbulletins
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Before a Palo Alto water heater is written off: what a repair can fix

Get quotes for water heater work in Palo Alto

Old chimneys near downtown, slabs and shallow roofs in the Eichler tracts

Faults a Palo Alto service call tends to find

A pilot that keeps going out

Too little hot water, or none

Water on the floor that is not a leak

A yellow flame or soot at the draft hood

A heat pump heater running on its elements